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Biomedical subjects

G K Lemasters

Publications and source records attributed to G K Lemasters.

At least 37 records · Page 2Linked to original sources
PubMed1993

Effects of occupational exposure to organic solvents and noise on hearing.

This study explored the effects of occupational exposure to solvents and noise on hearing. Interviews and hearing tests were conducted for printing and paint manufacturing workers. The experimental groups included unexposed (N = 50) workers and workers exposed to noise (N = 50), noise and toluene (N = 51), or an organic solvent mixture (N = 39). The risk of hearing loss was greater for the exposed groups than for the unexposed group. The adjusted relative risk estimates were four times greater [95% confidence interval (95% CI) 1.4-12.2] for the noise group, 11 times greater (95% CI 4.1-28.9) for the noise and toluene group, and five times greater (95% CI 1.4-17.5) for the solvent-mixture group. The findings suggest that exposure to the studied solvents had a toxic effect on the auditory system and that an interaction between noise and toluene took place. The audiological results of the noise and toluene group suggest a central auditory pathway involvement in the hearing losses observed.

Adult↗
PubMed1991

Fertility of workers chronically exposed to chemically contaminated sewer wastes.

Few studies have investigated the reproductive effects of exposure to chemical mixtures. The purpose of this study was to assess fertility in males exposed to mixed industrial and domestic wastes. A detailed reproductive history was obtained from the wives of 231 employees in order to evaluate fertility. Daily work records were used to define exposure status. To ascertain problems of infertility, the ratios of observed live births to expected live births (generated from U.S. birth probabilities) for exposed and nonexposed groups were calculated, and the ratios of these Standardized Fertility ratios (SRFs) were compared. Other analyses considered the couples' contraceptive history and preexposure versus postexposure experience. Though multiple statistical approaches were used to examine the data, the conclusion of this study was that exposure to chemical mixtures was not associated with a decrease in the couples' fertility.

Air Pollutants, Occupational↗
PubMed1991

Statistical issues in risk assessment of reproductive outcomes with chemical mixtures.

Establishing the relationship between a given chemical exposure and human reproductive health risk is complicated by exposures or other concomitant factors that may vary from pregnancy to pregnancy. Moreover, when exposures are to complex mixtures of chemicals, varying with time in number of components, doses of individual components, and constancy of exposure, the picture becomes even more complicated. A pilot study of risk of adverse reproductive outcomes among male wastewater treatment workers and their wives is described here. The wives of 231 workers were interviewed to evaluate retrospectively the outcomes of spontaneous early fetal loss and infertility. In addition, 87 workers participated in a cross-sectional evaluation of sperm/semen parameters. Due to the ever-changing nature of the exposure and the lack of quantification of specific exposures, six dichotomous variables were used for each specific job description to give a surrogate measure of exposure. Hence, no quantitative exposure-response relationships could be modeled. These six variables were independently assigned by two environmental hygienists, and their interrater reliability was assessed. Results are presented and further innovations in statistical methodology are proposed for further applications.

Data Interpretation, Statistical↗
PubMed1990

Work practices and policies of hospital pharmacists preparing antineoplastic agents.

Hospital-based female pharmacists were asked about workplace practices and conditions, use of protective equipment, and formal hospital guidelines governing exposure to antineoplastic agents. Special preparation areas dedicated to antineoplastic agents were absent in 13.4% of the workplaces. Vertical laminar flow hoods were unavailable for 27.7% of the respondents. Although protective gloves were worn by the majority (87.9%), safety glasses and facial masks were used infrequently. More than 40% of the group reported skin contact with cytotoxic drugs at least once a month. Eighty-three percent of all respondents reported that their institution had a formal policy governing the handling of antineoplastic agents. Medical surveillance for exposed employees, however, was available in only 28% of the workplaces.

Antineoplastic Agents↗
PubMed1989

Employment status as a confounder when assessing occupational exposures and spontaneous abortion.

Studies of occupational exposure and spontaneous abortion may use pregnancies during which the mother was unemployed as part or all of the unexposed comparison group. Any type of maternal employment, however, may be a risk factor for spontaneous abortion, and potential confounder in occupational reproductive studies. This study evaluates the effect of employment in a cohort of pregnancies of 1535 women. Employed pregnancies had a significantly higher rate of spontaneous abortion (14.5%) than unemployed pregnancies (11.7%) (RR = 1.23, 95% CI = 1.02, 1.49). Gravidity acted as an effect modifier, as the employment effect was seen only in multigravidous pregnancies (RR = 1.38, 95% CI = 1.11, 1.72) and not primigravidous pregnancies (RR = 0.96). The effect persisted when an independent sample of one randomly selected pregnancy per woman was used for the analysis (RR = 1.27, 95% CI = 0.90, 1.79). The data were examined for confounding by other factors which could explain the excess in spontaneous abortion among employed pregnancies. The employment effect persisted with adjustment for other risk factors including maternal age, education, income, maternal diabetes, race, alcohol usage and smoking, and prior pregnancy ending in induced abortion. Stratifying by prior pregnancy loss eliminated the employment effect among those with prior loss (RR = 1.03) but enhanced the effect among those multigravidous without the risk factor (RR = 1.50, 95% CI = 1.15, 1.97). Selection bias, also, was explored as a possible explanation of this employment effect, but could not be substantiated. Assessment of a true exposure effect requires consideration of a potential employment effect either in the design or analysis.

Abortion, Spontaneous↗
PubMed1989

Reproductive outcomes of pregnant workers employed at 36 reinforced plastics companies. II. Lowered birth weight.

The authors analyzed the birth weights of infants whose mothers worked during pregnancy in the reinforced plastics industry, where styrene monomer is a primary chemical exposure. Reproductive and work histories were taken by telephone interview from 1535 women employed between 1974 and 1981 at 36 companies. The questionnaire was based on one used by the National Institute for Occupational Safety and Health, and indices of styrene exposure were derived from an historical set of 1500 industrial hygiene samples from the study companies. There was not a significant dose-response trend in decreasing average birth weights. However, women who worked at the most highly exposed jobs--such as laminators, rollers, or spray-up operators at boat manufacturing companies--had offspring with adjusted birth weights of 4% less than the offspring of unexposed women (95% confidence interval = -7.7% to +0.6%) after adjustment for other factors.

Birth Weight↗
PubMed1987

The dose-response fallacy in human reproductive studies of toxic exposures.

The manner in which exposure is defined can affect the findings of reproductive studies of toxic exposures. The individual end points potentially examined, such as fetal loss, subfertility, and congenital malformations observed at birth, are on a continuum by severity of effect: The most extreme effect of the three being infertility because no pregnancy is possible, and the least extreme, congenital malformations recognized at birth. End points observed at birth are survivors of a long and complex process. The process yielding one of these adverse end points may result from a number of factors, including level of exposure. For example, a very high exposure could result in early fetal loss, whereas a lower one might result in a congenital malformation observed at birth. If the probability of a less severe end point falls due to increasing probability of more severe end points with increasing exposure, then a nontraditional dose-response relationship may be observed in the study of one type of outcome.

Dose-Response Relationship, Drug↗
PubMed1985

Statistical methods for describing occupational exposure measurements.

An important step in studies relating worker health to industrial exposure is the estimation of mean exposure levels. The investigator frequently has to rely on industrial hygiene measurements collected for other purposes. Samples may have been taken at several companies on different dates, and on each occasion multiple individual samplers may have been employed. Often it is not recognized that readings from such a hierarchical arrangement are correlated; for example, samples taken at the same time and location are more alike than samples taken on different days. This correlation invalidates the commonly used standard errors of sample means and the usual sample standard deviation. A component of variance analysis is suggested which quantifies within-day, between-day and between-company variation. Estimators of mean exposure are presented with correct standard errors. The techniques are illustrated by a small set of data and by a recent study of exposures to styrene in 36 companies manufacturing reinforced plastics.

Environmental Exposure↗
PubMed1985

Occupational styrene exposure for twelve product categories in the reinforced-plastics industry.

Approximately 1500 occupational styrene exposure values from 28 reinforced-plastic manufacturers were collected retrospectively from companies and state and federal agencies. This report describes the major types of manufacturing processes within the reinforced-plastics industry and reports on the availability, collection and analysis of historical exposure information. Average exposure to styrene in most open-mold companies (24-82 ppm) was generally 2-3 times the exposure in press-mold companies (11-26 ppm). Manufacturers of smaller boats had mean styrene exposures of 82 ppm as compared to 37 ppm for yacht companies. There was considerable overlap in styrene exposure among job titles classified as directly exposed within open- and press-mold processing.

Chemical Industry↗
PubMed1985

Reproductive outcomes in women exposed to solvents in 36 reinforced plastics companies. I. Menstrual dysfunction.

Recent studies have suggested that exposure to styrene monomer and other solvents is associated with menstrual disturbances. This is the first U.S. study to evaluate the effects of exposure to styrene on dysmenorrhea, intermenstrual bleeding, secondary amenorrhea, menstrual blood clots, and hypermenorrhea. A comprehensive questionnaire was administered to 1,535 blue-collar workers. Multiple logistic regression analyses did not reveal a positive association between styrene exposure and any menstrual abnormality. Risk factors associated with menstrual disturbances included chronic illness with secondary amenorrhea (p less than or equal to .005), nulliparity with both decreased blood clots (p less than or equal to .005) and hypermenorrhea (p less than or equal to .001), smoking with blood clots (p less than or equal to .005), and age with hypermenorrhea (p less than or equal to .001). The overall prevalences of menstrual disorders were 14% for dysmenorrhea, 16% for intermenstrual bleeding, 7% for secondary amenorrhea, 40% for menstrual blood clots, and 31% for hypermenorrhea.

Adult↗
PubMed1984

Use of exposure data in occupational reproductive studies.

Accurately characterizing worker exposure presents some unique problems in occupational reproductive studies. The latency period between exposure and the adverse event may be relatively brief - days, weeks, or months. Inaccurately identifying the specific exposure period which initiated the adverse event may then contribute to sizeable misclassification errors. This paper discusses different types of exposure models that can be used to help reduce misclassification and delineate the exposure-effect relationships more accurately. The advantages and disadvantages of exposure data sources are also discussed.

Female↗
PubMedDate not supplied

Assessment of reproductive disorders and birth defects in communities near hazardous chemical sites. I. Birth defects and developmental disorders.

Members of the workgroup on birth defects and developmental disorders discussed methods to assess structural anomalies, genetic changes and mutations, fetal and infant mortality, functional deficits, and impaired fetal and neonatal growth. Tier 1 assessments for all five adverse reproductive outcomes consist of questionnaires and reviews of medical records rather than laboratory testing of biologic specimens. The work-group members noted a role for neurodevelopmental testing and for limited genetic studies, such as karyotyping in Tier 2 assessments. Emerging methodologies to identify chromosomal aberrations, DNA adducts, and repair inhibition were reserved for Tier 3.

Adult↗
PubMedDate not supplied

Assessment of reproductive disorders and birth defects in communities near hazardous chemical sites. II. Female reproductive disorders.

Members of the workgroup on female reproductive disorders discussed methods to evaluate five principal functions: menstrual dysfunction, infertility, pregnancy loss, lactation disorders, and pregnancy complications. To test each function, a nested strategy was considered, based on progressive levels of effort available to conduct field investigations. This strategy was analogous to the three-tier classification of biomarkers used by other workshops. The lowest level of effort, corresponding to Tier 1, consists only of questionnaires, diaries, and reviews of maternal and infant medical records. The medium level of effort (Tier 2) collects data from questionnaires and diaries, and some biologic specimens. Suggested laboratory analyses included measurement of progesterone in saliva and several glycoprotein hormones in urine that evaluate menstrual dysfunction, infertility, and pregnancy loss. The highest level of effort (Tier 3) involves prospective collection of diary information and simultaneous collection of biological specimens.

Abortion, Spontaneous↗
PubMedDate not supplied

Male reproductive effects of solvent and fuel exposure during aircraft maintenance.

Few studies have addressed the effects of mixed, low-level exposures to complex mixtures on a man's reproductive potential. In this prospective study, each subject was evaluated before first exposure and at 15 and 30 weeks after exposures had begun. A total of 50 men working on aircraft maintenance at an Air Force installation were included in the study. In addition, eight unexposed men were concurrently sampled. Industrial hygiene (IH) sampling and expired breath samples were collected for jet fuel as measured by total napthas, benzene--a component of jet fuel, 1,1,1-trichloroethane, methyl ethyl ketone, xylenes, toluene, and methylene chloride. Sperm production, structure, and function (sperm concentration, sperm motion, viability, morphology, morphometrics, and stability of sperm chromatin) were evaluated. Exposures were low. All mean IH measures were below 6 ppm, which is less than 10% of the Occupational Safety and Health Administration standard for all chemicals except benzene. Sheet metal workers had the highest mean breath levels for both total solvents (24 ppb) and fuels (28.3 ppb). For most sperm measures, mean values remained in the normal range throughout the 30 weeks of exposure. When jobs were analyzed by exposure groups, some adverse changes were observed. The paint shop group had a significant decline in motility of 19.5% at 30 weeks. Internal dose measures, however, did not show a significant association with spermatogenic changes.

Adult↗
PubMedDate not supplied

A distraction technique for control of burn pain.

Research has indicated that analgesics alone do not adequately relieve pain for 75% of patients with burns. The purpose of this study was to determine the effects of a distraction therapy, in which videos were used in combination with administration of analgesics, on intensity and quality of pain and on levels of anxiety in adults during burn dressing changes. The sample consisted of 17 patients who were randomly assigned to the treatment or the control group. The treatment group viewed video programs that were composed of scenic beauty accompanied by music. Each was asked to score his or her present pain intensity and pain rating index with the McGill questionnaire and anxiety with the Spielberger questionnaire before and after the dressing change. A nested general linear model using the "F" test in multiple regression analysis was adjusted for age, percent partial-thickness burn, and choice of topical agent demonstrated that the use of videos during the dressing changes significantly reduced pain and anxiety: present pain intensity (F = 8.69; p = 0.01), pain rating index (F = 5.57; p = 0.03), anxiety (F = 9.10; p = 0.01). It is recommended that the use of pain medication be augmented by use of videos during burn dressing changes.

Adult↗
PubMedDate not supplied

Zinc insufficiency during pregnancy. A review.

Zinc deficiency has been found to cause problems in parturition and in the growth and development of the offspring. There are several groups of pregnant women at known risk of developing a zinc insufficiency; these include vegetarians, alcoholics, teenagers, women with multiple pregnancies, and women with impaired intestinal absorption of zinc. Nurses need to be able to identify the population at risk and to offer dietary counseling.

Animals↗